"I was drunk and got lost in the building. I wandered into an attic room and Karl was there. I got really embarrassed and apologized, but he said, 'No, come in.' We had a chat -- although I can't remember what about, I was so drunk. I do remember asking him about some shoes he'd designed that had a green ring in the heel [from Chanel's Fall 2009 collection]. I asked how they worked. He drew a diagram explaining the physics of making the shoe. I've still got the drawing. A week later I was asked to do the campaign."

Aside from her ongoing relationship with Chanel (she's a front-row fixture and has performed at Lagerfeld's shows), Allen is further exploring her love of fashion with her own vintage clothing shop, Lucy in Disguise, which will open in London this September. Just don't expect the shop to stock all of the Chanel that Allen has recently collected.

"When I'm buying expensive things I tend to think, 'Yep, that's something timeless that I can give to my daughter,'" Allen tells the glossy, before shooting off more baby-hungry thoughts.

"I don't think I'm that young to have a baby. My mother had me when she was 23," Allen, who is in a serious relationship with 31-year-old architect and interior designer Sam Cooper, says. In fact, she tells the magazine she has no problem putting her music career on hold and focusing on the shop and parenting instead.

"It's difficult as a woman who wants a family. Kids take up your whole life, particularly in the first two or three years," she says. "So it wouldn't be very responsible of me to commit to doing a world tour if I had a baby."

Although not being on tour means she'll lose a little muscle.

"When I was on tour earlier in the year, I'd be on stage for one-and-a-half hours a night, so since the tour finished in March, I've put on about half a stone," she says. "But I do Pilates three times a week. I am still body conscious, but I'm not so concerned with it. I don't care as much."

A particularly good mindset to be in when thinking about pregnancy.

To read more of UK Elle's exclusive interview and see more photos from the fashion shoot with Allen, pick up the August issue July 3.